This invention relates to a catalyst that can be used for hydrorefining and hydrocracking of hydrocarbon feedstocks under hydrogen pressure, whereby said catalyst comprises at least one zeolite (preferably a Y or beta zeolite) and at least one oxide matrix, whereby the zeolite contains in its porous network at least one metal of group VB (group 5 according to the new notation of the periodic table: Handbook of Chemistry and Physics, 76th Edition, 1995-1996), (preferably niobium) and optionally at least one noble or non-noble metal of group VIII (groups 8, 9 and 10) of said classification, preferably cobalt, nickel and iron. The oxide matrix contains at least one metal of group VIB, advantageously molybdenum and tungsten, and/or at least one metal of group VIII, advantageously cobalt, nickel and iron, and/or at least one metal of group VB, preferably niobium. The catalyst also contains at least one promoter element (phosphorus, boron, silicon).
This invention also relates to the processes for preparation of said catalyst, as well as its use for the hydrocracking of hydrocarbon feedstocks, such as the petroleum fractions and the fractions that are obtained from carbon containing sulfur and nitrogen in the form of organic compounds, whereby said feedstocks optionally contain metals and/or oxygen.
Conventional hydrocracking of petroleum fractions is a very important refining process that makes it possible to produce, starting from excess heavy hydrocarbon feedstocks, lighter fractions such as gasolines, kerosenes and light gasoils that the refiner seeks to adapt his production to the structure of the demand. Relative to the catalytic cracking, the advantage of catalytic hydrocracking is to provide more selectively middle distillates, kerosenes and gasoils of very good quality.
The catalysts that are used in conventional hydrocracking are all of bifunctional type that link an acid function to a hydrogenating function. The acid function is generally provided by crystallized aluminosilicate-type substrates that are called zeolites. The hydrogenating function is provided either by one or several metals of group VIII of the periodic table, such as iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum, or by a combination of at least one metal of group VI of the periodic table, such as chromium, molybdenum and tungsten, and at least one metal of group VIII, in general a non-noble metal such as Co, Ni and Fe.
The pure or dealuminified zeolite-type substrates that are, for example, of Y type or else beta type have a very strong acidity. These substrates therefore ensure the acid function of the hydrocracking catalysts. These systems are therefore active, and the products that are formed are of good quality. The drawback of these zeolite-based catalytic systems is a degradation of the selectivity of middle distillates (gasoil+kerosenes) when the amount of zeolite is increased. This therefore limits the amount of zeolite that can be used in the catalyst and therefore the level of activity that can be achieved while maintaining a good selectivity of middle distillate.
The applicant discovered that to obtain a hydrocracking catalyst that has strong activity and good selectivity of middle distillates, it is advantageous to provide a promoter element and to introduce into the porous network of the zeolite a hydrogenating phase that thus comes to reinforce the hydrogenating phase that is present in the oxide matrix, and it is also advantageous to use a large amount of zeolite. A hydrogenating function that is introduced into the zeolite can be ensured by at least one element or element compound of group VB such as niobium, at least one element of group VIB and/or at least one element of group VIII. The element of group VB can advantageously be associated with at least one metal or metal compound of group VIII. It is advantageously possible to use a combination of metals of group VB and optionally a combination of metals of group VIII.
More specifically, the invention relates to a catalyst that contains at least one matrix, at least one zeolite and at least one element that is located at the matrix (i.e., deposited on the catalyst or contained in the matrix), and selected from the group that is formed by the elements of groups VIB, VIII and VB and at least one promoter element that is selected from the group that is formed by phosphorus, boron, and silicon, whereby the zeolite contains in its porous network at least one element of group VB.
The catalyst of this invention generally contains in % by weight relative to the total mass of the catalyst:
0.1 to 99%, or 0.1-98.8%, or else 0.1 to 95% and preferably 0.1-90% and even 0.1-85%, of at least one zeolite, preferably a Y zeolite or a beta zeolite, advantageously the zeolite content is at least 5%, preferably at least 15%, and even at least 20%,
1 to 99.7%, or 1 to 97.9%, preferably 10 to 95% and even more preferably 15 to 95% of at least one amorphous oxide matrix, preferably an alumina, a silica or a silica-alumina,
0.1 to 40%, or 0.1-40%, advantageously 1 to 40%, preferably 1.5 to 35% and even more preferably 2 to 30% of at least one metal of group VB (expressed by weight of oxide),
0 to 40%, advantageously 1 to 40%, preferably 1.5 to 35% and even more preferably 2 to 30% of at least one metal of group VIB (expressed by weight of oxide),
0 to 30%, advantageously 0.1 to 30%, preferably 0.1 to 25% and even more preferably 0.1 to 20% of at least one metal of group VIII (expressed by weight of oxide),
at most 20%, or else 0.1-20%, preferably 0 to 15% and even more preferably 0 to 10% (expressed by weight of oxide), of at least one promoter element that is selected from the group that is formed by boron, phosphorus, silicon (not including the silicon that is contained in the zeolite),
and optionally 0-20%, preferably 0.1-15%, or else 0.1-10% of at least one element that is selected from group VII A, preferably fluorine, and the zeolite contains in its porous system (expressed by weight of oxide in the catalyst):
0.1 to 10%, preferably 0.1 to 7%, and even more preferably 0.1 to 5% by weight of oxide of at least one metal of group VB, and optionally,
0 to 10%, preferably 0 to 7%, and even more preferably 0 to 5% by weight of oxide of at least one metal of group VIII and/or at least one metal of group VIB, whereby a content of at least 0.1% is advantageous.
The metal of group VB that is contained in the porous network of the zeolite can be the same or different from the one that is contained in the matrix. In the same way, the metal of group VIII that is contained in the zeolite can be the same or different from the one that is contained in the matrix.
The demonstration of the presence of the hydrogenating phase in the porous network of the zeolite can be carried out by various methods that are known to one skilled in the art such as, for example, the electronic microprobe and the electronic transmission microscopy equipped with an X energy dispersion spectrometer with a detector that allows the identification and the quantification of elements that are present in the crystals of the zeolite and in the oxide matrix.
The catalyst of this invention has a very high hydrocracking activity of the hydrocarbon fractions and a greater selectivity than the catalytic formulas that are known in the prior art. Without subscribing to any particular theory, it seems that this particularly high activity of the catalysts of this invention is due to the joint presence of a hydrogenating function at the matrix and an element of group VB within the porous network of the zeolite, in combination with the presence of a promoter element.
The hydrogenating function on the matrix is ensured by at least one element of groups VIII, VIB, VB and preferably by at least one element of GVIB or advantageously by an element of GVIII, preferably a non noble element (Co, Ni). A combination of at least one element of GVIII and at least one element of GVIB preferably will be used.
The promoter element is mainly located on the matrix. The silicon promoter element is thus in amorphous form and is located mainly on the matrix.
The silicon that is introduced and that is mainly located on the substrate matrix can be characterized by techniques such as the Castaing microprobe (distribution profile of various elements), the electronic microscopy by transmission coupled to an X analysis of the components of the catalysts, or else by the establishment of a cartography for distribution of the elements that are present in the catalyst by electronic microprobe. These local analyses will provide the location of various elements, in particular the location of the amorphous silica on the matrix caused by the introduction of silicon. The location of the silicon of the framework of the zeolite is also revealed. Furthermore, a quantitative estimation of the local contents of silicon and other elements can be made.
In contrast, the NMR of the solid of 29Si with rotation at the magic angle is a technique that makes it possible to detect the presence of amorphous silica that is introduced into the catalyst according to the operating procedure that is described in this invention.
The catalyst of this invention can be prepared by all of the methods that are well known to one skilled in the art.
More specifically, a preparation method comprises the following stages:
a) Introduction into the zeolite of at least one element of group VB and optionally at least one element of group VIII and/or VIB,
b) mixing with the matrix and shaping to obtain the substrate;
c) introduction of at least one promoter element by impregnation and introduction of at least one element of groups VIB, VIII and VB into the matrix or on the substrate by at least one of the following methods:
addition of at least one compound of said element during the shaping to introduce at least a portion of said element,
impregnation of the substrate with at least one compound of said element or ionic exchange on the calcined substrate with a solution of at least one compound of group VIII;
d) drying and calcination of the final product that is obtained and optionally drying and/or calcination of the products that are obtained at the end of stages a) or b) or after an impregnation.
Advantageously, the catalyst of this invention is prepared according to the following three stages:
a) Introduction of at least one metal of group VB and optionally at least one metal of group VIII and/or VIB into the zeolite optionally followed by drying and calcination or calcination without prior drying. The drying can be carried out at a temperature of between 60 and 250xc2x0 C. and the calcination at a temperature of 250 to 800xc2x0 C.
b) Shaping of the mixture of the zeolite that contains the metal of group VB and optionally the metal of group VIII obtained in stage a) with the oxide matrix to obtain the substrate. One of the preferred methods for shaping in this invention consists in mixing the zeolite in a moist alumina gel for several tens of minutes, then in passing the paste that is thus obtained through a die to form extrudates with a diameter of preferably between 0.4 and 8 mm. The introduction of the elements of group VB and/or VIB and/or VIII, not including in the zeolite, can take place optionally in this stage by addition of at least one compound of said element so as to introduce at least a portion of said element. This introduction can be accompanied by that of phosphorus, boron, and/or silicon and optionally that of the element of group VIIA (fluorine, for example). The solid that is shaped is then optionally dried at a temperature of between 60 and 250xc2x0 C. and calcined at a temperature of 250 to 800xc2x0 C.
c) Introduction of the elements of group VB and/or VIB and/or VIII, and promoter element (such as phosphorus), optional element of group VIIA by deposition on the substrate (calcined or dried and preferably calcined) that is obtained in stage b), when they have not been introduced completely during stage b). A deposition method that is well known to one skilled in the art is the impregnation of the substrate by a solution that contains the elements of group VB and/or VIB and/or VIII, and a promoter element (such as phosphorus). The deposition is then optionally followed by drying at a temperature of between 60 and 250xc2x0 C. and optionally by calcination at a temperature of between 250 to 800xc2x0 C.
The oxide matrix is usually selected from the group that is formed by the transition aluminas, the silicas and the silica-aluminas and mixtures thereof. It is preferred to use matrices that contain alumina, in all of its forms that are known to one skilled in the art, for example the gamma-alumina.
The preferred zeolite source is the Y zeolite or else the beta zeolite in all of their forms. The zeolite can be in hydrogen form or at least partially exchanged with metallic cations, for example with cations of alkaline-earth metals and/or cations of rare earth metals of atomic number 57 to 71 inclusive. The zeolite can be at least partly (i.e., more or less) dealuminified as is well known to one skilled in the art.
The element sources of group VIB that can be used are well known to one skilled in the art. For example, among the sources of molybdenum and tungsten, the oxides and the salts of ammonium such as ammonium molybdate, ammonium heptamolybdate and ammonium metatungstate are preferably used.
The element sources of group VB that can be used are well known to one skilled in the art. For example, among the sources of niobium, it is possible to use oxides, such as diniobium pentaoxide Nb2O5, niobic acid Nb2O5.H2O, niobium hydroxides and polyoxoniobates, the niobium alkoxides of formula Nb(OR1)3 where R1 is an alkyl radical, niobium oxalate NbO(HC2O4)5, ammonium niobate. Niobium oxalate or ammonium niobate is preferably used.
The element sources of group VIII that can be used are well known to one skilled in the art. For example, nitrates, sulfates, and halides will be used.
The preferred phosphorus source is orthophosphoric acid H3PO4, but its salts and esters such as the ammonium phosphates are also suitable. Phosphomolybdic acid and its salts, and phosphotungstic acid and its salts can also advantageously be used. The phosphorus can be introduced, for example, in the form of a mixture of phosphoric acid and a basic organic compound that contains nitrogen, such as ammonia, primary and secondary amines, cyclic amines, compounds of the family of pyridine and quinolines and the compounds of the family of pyrrole.
A number of silicon sources can be used. It is thus possible to use ethyl orthosilicate Si(OEt)4, siloxanes, polysiloxanes, silicones, silicone emulsions, halide silicates such as ammonium fluorosilicate (NH4)2SiF6 or sodium fluorosilicate Na2SiF6. The silicomolybdic acid and its salts, and silicotungstic acid and its salts can also advantageously be used. Silicon can be added by, for example, impregnation of ethyl silicate in solution in a water/alcohol mixture. The silicon can be added by, for example, impregnation of a silicone-type silicon compound that is suspended in water.
The boron source can be boric acid, preferably orthoboric acid H3BO3, ammonium biborate or pentaborate, boron oxide, or boric esters. Boron can be introduced, for example, in the form of a mixture of boric acid, oxidized water and a basic organic compound that contains nitrogen, such as ammonia, primary and secondary amines, cyclic amines, compounds of the family of pyridine and quinolines and the compounds of the family of pyrrole. Boron can be introduced by, for example, a boric acid solution in a water/alcohol mixture.
The sources of elements of group VIIA that can be used are well known to one skilled in the art. For example, the fluoride anions can be introduced in the form of hydrofluoric acid or its salts. These salts are formed with alkaline metals, ammonium or an organic compound. In this latter case, the salt is advantageously formed in the reaction mixture by reaction between the organic compound and the hydrofluoric acid. It is also possible to use hydrolyzable compounds that can release fluoride anions into water, such as ammonium fluorosilicate (NH4)2SiF6, silicon tetrafluoride SiF4 or sodium tetrafluoride Na2SiF6. Fluorine can be introduced by, for example, impregnation of an aqueous solution of hydrofluoric acid or ammonium fluoride.
The hydrogenating function relative to the matrix as it was defined above can therefore be introduced into the catalyst at various levels of the preparation and in various ways. It can be introduced in part only (case, for example, of the combinations of metal oxides of groups VI and VIII) or completely at the time of mixing of the source of alumina and zeolite in stage b), whereby the remainder of the hydrogenating element(s) is then introduced after mixing, and more generally after calcination. The metal of group VIII is preferably introduced simultaneously or after the metal of group VI, regardless of the method of introduction.
The hydrogenating function relative to the matrix can also be introduced by one or more ion exchange operations onto the calcined substrate (zeolite that is dispersed into the alumina matrix), with solutions that contain the precursor salts of metals that are selected when the latter belong to group VIII. The hydrogenating function (element of group VIII) is then located both in the porous network of the zeolite and in the matrix. In this case, it is conceivable to limit the amount of metal of group VIII that is introduced into the zeolite before its shaping.
The hydrogenating function relative to the matrix can also be introduced by one or more operations for impregnation of the substrate that is shaped and calcined, by a solution of the precursors of the oxides of metals of group VIII when the precursors of the oxides of metals of group VIB and/or of group VB were previously introduced at the time of the mixing of the substrate.
The hydrogenating function relative to the matrix can finally be introduced by one or more operations for impregnation of the calcined substrate that consists of the zeolite and the alumina matrix that is optionally doped by P, by solutions that contain the precursors of the oxides of metals of groups VIB, VB and/or VIII, whereby the precursors of oxides of metals of group VIII are preferably introduced after those of groups VB and VIB or at the same time as the latter.
In the case where the elements are introduced in several impregnations of the corresponding precursor salts, an intermediate calcination stage of the catalyst should be carried out at a temperature of between 250 and 600xc2x0 C.
The introduction of phosphorus, boron and/or silicon into the catalyst can be carried out at various levels of the preparation and in various ways. A preferred method according to the invention consists in preparing an aqueous solution of at least one element of group VI and/or at least one element of group VB and/or at least one element of group VIII and a compound of phosphorus, boron and/or silicon and in initiating a so-called dry impregnation, in which the volume of the pores of the precursor is filled by the solution.
The impregnation of molybdenum and/or tungsten can be facilitated by the addition of phosphoric acid into the solutions, which makes it possible also to introduce phosphorus so as to promote the catalytic activity. Other compounds of the phosphorus can be used as is well known to one skilled in the art.
Phosphorus, boron and/or silicon can be introduced by one or more impregnation operations with excess solution in the calcined precursor.
A preferred method consists in depositing, for example by impregnation, the selected promoter element or elements, for example the boron-silicon pair, on the precursor that may or may not be calcined but is preferably calcined. For this purpose, an aqueous solution is prepared from at least one boron salt such as ammonium biborate or ammonium pentaborate in an alkaline medium and in the presence of oxidized water, and a so-called dry impregnation is initiated in which the volume of the pores of the precursor is filled by the solution that contains boron. In the case where, for example, silicon is deposited, for example a solution of a silicone-type silicon compound will be used.
The deposition of boron and silicon can also be done simultaneously by using, for example, a solution that contains a boron salt and a silicone-type silicon compound. Thus, for example, it is possible to impregnate by an aqueous solution of ammonium biborate and Rhodorsil E1P silicone of the Rhxc3x4ne-Poulenc Company, to initiate drying at, for example, 80xc2x0 C., then optionally to impregnate by an ammonium fluoride solution, to initiate drying at, for example, 80xc2x0 C., and to initiate calcination for example preferably under air in a flushed bed, for example at 500xc2x0 C. for 4 hours.
A particular preparation comprises:
a) Introduction of niobium into the zeolite,
b) mixing with the matrix, shaping, and calcination,
c) impregnation of the calcined substrate with a solution of at least one compound of nickel, at least one compound of molybdenum and at least one promoter element (phosphorus, for example),
d) drying, and calcination.
The catalysts that are obtained by this invention are shaped in the form of grains of different shapes and sizes. They are generally used in the form of cylindrical or multilobar extrudates, such as bilobar, trilobar, multilobar extrudates of straight or twisted shape, but they can optionally be produced and used in the form of crushed powder, tablets, rings, balls, and wheels. They have a specific surface area that is measured by nitrogen adsorption according to the BET method (Brunauer, Emmett, Teller, J. Am. Chem. Soc., Vol. 60, 309-316 (1938)) that is greater than 100 m2/g, a pore volume that is measured by mercury porosimetry of between 0.2 and 1.5 cm3/g and a size distribution of pores that can be monomodal, bimodal or polymodal. The catalysts of this invention preferably have a distribution of monomodal pores.
Use for the Transformation of Hydrocarbon Fractions
The catalysts that are thus obtained are generally used for hydrocracking in particular distillate-type hydrocarbon fractions (kerosene, gasoil), vacuum distillates, deasphalted residues or the equivalent, whereby the fractions optionally first can be hydrotreated.
The treated hydrocarbon feedstocks have initial boiling points of at least 150xc2x0 C., preferably at least 350xc2x0 C., and more advantageously it is a boiling fraction of between 350 and 620xc2x0 C.
The hydrocracked fractions with the catalyst of the invention are preferably such that at least 80% by volume corresponds to compounds whose boiling points are at least 320xc2x0 C. and preferably between 350 and 620xc2x0 C. (i.e., corresponding to compounds that contain at least 15 to 20 carbon atoms). They generally contain heteroatoms such as sulfur and nitrogen. The nitrogen content is usually between 1 and 5000 ppm by weight, and the sulfur content is between 0.01 and 5% by weight.
The hydrocracking conditions such as temperature, pressure, hydrogen recycling rate, hourly volumetric flow rate, can be very variable based on the nature of the feedstock, the quality of the desired products and the installations used by the refiner. The temperature is generally higher than 200xc2x0 C. and often between 250xc2x0 C. and 480xc2x0 C. The pressure is greater than 0.1 MPa and often greater than 1 MPa. The hydrogen recycling rate is at least 50 normal liters of hydrogen per liter of feedstock and often between 80 and 5000 normal liters of hydrogen per liter of feedstock. The hourly volumetric flow rate is generally between 0.1 and 20 volumes of feedstock per volume of catalyst and per hour.
The catalyst of this invention can be used in various cases of the hydrocracking process that link one or more reactors in a series with intermediate separation or otherwise, with recycling of the residue or otherwise.
The catalyst can be used in any hydrocracking process that is known to one skilled in the art, such as, for example, the processes in one stage, with one or more catalysts with or without recycling of gases and liquid or in two stages with one or more catalysts with or without separation between the two reactors with or without recycling of the gases and liquid.
The catalysts of this invention are preferably subjected to a sulfurization treatment that makes it possible to transform, at least in part, the metallic radicals into sulfides before they are brought into contact with the feedstock that is to be treated. This activation treatment by sulfurization is well known to one skilled in the art and can be carried out by any method that is already described in the literature.
A standard sulfurization method that is well known to one skilled in the art consists in heating, in the presence of hydrogen sulfide, to a temperature of between 150 and 800xc2x0 C., preferably between 250 and 600xc2x0 C., generally in a flushed-bed reaction zone.
The catalyst of this invention preferably can be used for hydrocracking fractions (such as those of vacuum distillate type) that are high in sulfur and nitrogen and that were previously hydrotreated. In this case, the petroleum fraction conversion process takes place in two stages, whereby the catalyst according to the invention is used in the second stage.
Catalyst 1 of the first stage has a hydrotreatment function and comprises a matrix that preferably has an alumina base and preferably does not contain zeolite, and at least one metal that has a hydrogenating function. Said matrix can also consist of or contain silica, silica-alumina, boron oxide, magnesia, zirconia, titanium oxide or a combination of these oxides. The hydro-dehydrogenating function is ensured by at least one metal or metal compound of group VIII, such as nickel and cobalt in particular. It is possible to use a combination of at least one metal or metal compound of group VI (in particular molybdenum or tungsten) and at least one metal or metal compound of group VIII (in particular cobalt or nickel) of the periodic table. The total concentration of oxides of metals of groups VI and VIII is between 5 and 40% by weight and preferably between 7 and 30% by weight, and the ratio by weight that is expressed in terms of metal oxide of metal (or metals) of group VI to metal (or metals) of group VIII is between 1.25 and 20 and preferably between 2 and 10. In addition, this catalyst can contain phosphorus. The phosphorus content, expressed by concentration of diphosphorus pentaoxide P2O5, will generally be at most 15%, preferably between 0.1 and 15% by weight and preferably between 0.15 and 10% by weight. It can also contain boron in a B/P ratio=1.02-2 (atomic), whereby the sum of B and P contents expressed in oxides is 5-15% by weight.
The first stage takes place generally at a temperature of 350-460xc2x0 C., preferably 360-450xc2x0 C., a pressure of greater than 2 MPa, and preferably greater than 5 MPa, an hourly volumetric flow rate of 0.1-5 hxe2x88x921 and preferably 0.2-2 hxe2x88x921, and with an amount of hydrogen of at least 100 Nl/Nl of feedstock and preferably 260-3000 Nl/Nl of feedstock.
For the conversion stage with the catalyst according to the invention (or second stage), the temperatures are generally greater than or equal to 230xc2x0 C. and often between 300xc2x0 C. and 430xc2x0 C. The pressure is generally greater than 2 MPa and preferably greater than 5 MPa. The amount of hydrogen is at least 100 l/l of hydrogen and often between 200 and 3000 l/l of hydrogen per liter of feedstock. The hourly volumetric flow rate is generally between 0.15 and 10 hxe2x88x921.
Several hydrocracking methods can be used. In a first hydrocracking method, the pressure is moderate. The catalyst according to the invention is then used at a temperature that is generally greater than or equal to 230xc2x0 C. or 300xc2x0 C., generally at most 480xc2x0 C. and often between 350xc2x0 C. and 450xc2x0 C. The pressure is generally greater than 2 MPa and less than or equal to 12 MPa. A range of moderate pressure is particularly advantageous that is 7.5-11 MPa, preferably 7.5-10 MPa or else 8-11 MPa and advantageously 8.5-10 MPa. The amount of hydrogen is at least 100 normal liters of hydrogen per liter of feedstock and often between 200 and 3000 normal liters of hydrogen per liter of feedstock. The hourly volumetric flow rate is generally between 0.1 and 10 hxe2x88x921.
In a second embodiment, the catalyst of this invention can be used for hydrocracking under high hydrogen pressure conditions of at least 8.5 MPa, preferably at least 9 MPa or at least 10 MPa. The treated fractions are, for example, of vacuum distillate type and are high in sulfur and nitrogen and have been previously hydrotreated. In this case, the petroleum fraction conversion process generally takes place in two stages, whereby the catalyst according to the invention is used in the second stage.
For the conversion stage with the catalyst according to the invention, the temperatures are generally greater than or equal to 230xc2x0 C. and often between 300xc2x0 C. and 430xc2x0 C. The pressure is generally greater than 8.5 MPa and preferably greater than 10 MPa. The amount of hydrogen is at least 100 l/l of feedstock and often between 200 and 3000 l/l of hydrogen per liter of feedstock. The hourly volumetric flow rate is generally between 0.15 and 10 hxe2x88x921.
Conversion levels that are higher than those obtained in the first method described above then are attained.
Under these conditions, the catalysts of this invention have a better conversion activity and a better selectivity of middle distillates than the commercial catalysts.
The catalyst according to the invention can also be used for hydrorefining (HDS, HDN and hydrogenation in particular). The temperature is generally higher than 200xc2x0 C. and often between 280xc2x0 C. and 480xc2x0 C. The pressure is generally higher than 0.1 MPa and often higher than 1 MPa. The presence of hydrogen is generally necessary with a hydrogen recycling rate that is generally at least 80 and often between 100 and 4000 liters of hydrogen per liter of feedstock. The hourly volumetric flow rate is generally between 0.1 and 20 hxe2x88x921.